Folding knife



FIG. 1 is a front elevational view of a folding knife showing my design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a rear elevational view thereof with the knife in a folded position;

FIG. 4 is a front elevational view thereof with the knife in a folded position; and,

FIG. 5 is a top plan view thereof. 

The ornamental design for a folding knife, as described and shown. 